1. Field of the Invention
The present invention relates to a buckle for tightening a belt comprising a female member formed with a flat housing and a male member having a pair of flexible insertion legs, in which a pair of the flexible insertion legs of the male member are inserted into the housing of the female member and engaged therein.
2. Description of the Related Art
A conventional insertion type buckle comprising a female member, that is, female body, formed with a flat housing and a male member, that is, male body, having a pair of flexible insertion legs is well-known to have a butting portion of the female body and the male body, which is formed in a simple straight form when the female body and the male body are engaged. As shown in FIG. 28, a buckle of a type to finish an insertion opening 7′ of the flat housing 3′ of the female body 1′ into a straight form, bring a front end of a side frame on each of both sides in the frame 20′ of the belt through portion into contact with the insertion opening 7′ edge of the housing 3′ in the male body 2′, and butt both members each other, is well-known. This kind of buckle is disclosed, for example, in Japanese Patent Application Laid-Open No. 9-135609.
Furthermore, as shown in FIG. 29, a buckle comprising a female body 1″ formed with a flat housing 3″ and a male body 2″ having a pair of insertion legs 30″, in which the butting portions 15″, 38″ of the female body 1″ and the male body 2″, when the insertion legs 30″ of the male body 2″ is inserted into the housing 3″ of the female body 1″ in an insertion form, are slightly cut off in a curved form at both ends of the female body 1″ and formed to slightly protrude in an arcuate form at both ends of the male body 2″. Then, the relevant ends are connected at a central straight portion is disclosed in U.S. Pat. No. 5,590,444.
In the conventional buckle described above in which the insertion opening of the housing of the female body and the base of the insertion legs of the male body are formed in a straight line and a butting surface between the female body and the male body is also formed in a straight line. In the buckle shown in FIG. 28, the insertion opening 7′ of the housing 3′ of the female body 1′ is formed in a straight line, and in the male body 2′, the front ends of both side frames in the frame 20′ of the belt through portion are brought into contact with the insertion opening 7′. As for the buckles described above, the buckles may clatter and lack stability when the female body 1′ and the male body 2′ are engaged by insertion, and further, no smooth inserting operation is expected only with the guide member 35′ at the center when the insertion legs 30′ are inserted into the housing.
In the buckle shown in FIG. 29, because the butting surface between the female body 1″ and the male body 2″ is held by the bent portions at the ends on both sides of the buckle when the insertion legs 30″ of the male body 2″ is inserted into the housing 3″ of the female body 1″, there is such a problem that any clearance on the right and left causes the female body 1″ and the male body 2″ to slip and results in clattering.